THE GREAT AMERICAN DESERT 



213 



even the heaviest downpour. Because of the general porous nature of 

 the soil the region is characterized by sub-surface drainage. The fluc- 

 tuations in the ground water from time to time produce differences in 

 the level of the lakes and ponds. During especially wet seasons the 

 level of the lakes may be perceptibly elevated, due in all probability to 

 seepage from the surrounding hills. 



The most important stream of the Sand Hills is the Loup Eiver, the 

 three forks of which rise in low swampy flats toward the central portion 

 of the region. Through the Sand Hills portion of its course the Middle 

 Loup has a fall of about eight feet per mile and so develops considerable 

 current which causes its bed and its channel to shift continually. The 

 sand banks are cut and the channel veers from side to side along its 

 course. This tendency culminates in the formation of many " oxbows " 



Fig. 1. The Middle Loup River with Fringes of Woody Vegetation. 



Sand Hills in the distance. 



or loops. Some of these loops are most perfect and beautiful as viewed 

 from far up in the hills. The streams of the region are all shallow, the 

 Loup varying from one to six feet in depth with a channel about fifty 

 yards wide. In many places such streams are extremely beautiful with 

 their winding channels of clear swift water and fringes of vegetation. 

 The Dismal Eiver is an important tributary to the Loup. Heading 

 in the swamp and lake region of Hooker, Grant and McPherson counties, 

 it continues eastward for about seventy-five or eighty miles, and pours 

 into the Loup at Dunning. This river is an especially welcome sight as 



